Severian

Negative now then, is it?

I haven't. Maybe I am frequenting the wrong clubs.

That cloud is not a star. It is two colliding clusters of galaxies. This is much much bigger scale.

Observationally, I don't think there would be any problem with having a big ball of pure antimatter out there in the universe. It would have to be either dark (ie. uncharged particle not radiating light) or small enough that we just haven't noticed it. It wouldn't just annihilate because the space is such a good vacuum - there is nothing to annihilate with. In fact, quite a good question might be, how do we know that (some of) the stars we see are not made of antimatter? I am not sure I know the answer to that. (Of course, from a theoretical point of view it doesn't really work without having a mechanism to separate the matter and antimatter into solar systems.)

I think the problem most people are having with this stems from the idea of the big bang happening at a point. It didn't - at least not in the sense that people think of a point. The big bang happened everywhere at once. We only say 'a point' because in the limit of [math]t \to 0[/math] all distance scales shrink to zero and there is no distance between anything in the galaxy. So you think of everything being in the same place. But this is just a limit and probably isn't very physical. At [math]t=\epsilon[/math] where [math]\epsilon[/math] is vanishingly small, there were already finite distance scales and the universe had infinite extent.

I know 'astrophysicists' who get offended if you call them 'astronomers'. I'm buggered if I know the difference. I am also slightly bemused by why so many universities have a 'Department of Physics & Astronomy". Isn't Astronomy a subset of physics?

Sure, I think I would rate Steven Weinberg as a great scientist. There are plenty of other great scientists who are atheists too.

er... which bit did you not understand?

That was why I said: "either can't have them, or always have them, depending on your point of view." But since these equations I am talking about are the fundamental Lagrangians, and there is no observable difference, there can be no observable difference in any process. So there can be no "way to use" them at all.

I think that is true. I would even go so far as to say that maths is just a language for expressing logic in an efficient way. When we find some new logical system that we can't describe with current maths, we make up some new words/symbols/axioms to describe it mathematically.

Lol! Now I have seen it all. 1veedo is basically trying to argue that Dawkins is a "one of the world's greatest scientists of all time" by changing the definition of "greatest scientist".

I think the maths reference is a bit of a red herring. If a theory is makes predictions then it must be describable by maths, and must be conceptualizable. If it cannot be described by maths, then it is not predictive and is not science. In other words, the only non-conceptualizable phenomena would be non-predictive phenomena, where you could never set about making predictions not even on a statistical level with 100% knowledge of the initial state.

It is not the discontinuity which is a problem. After all, you don't have to imagine this as gravity. You could have some hypothetical potential which was like gravity on one side of the line and zero on the other, and just because we don't know how to make it does not invalidate your argument. It shouldn't be discontinuous, but a very steeply varying function which goes from 0 to your required value within the width of a superstring would do fine. The problem is that you are actually missing an energy in your calculation. Since the field is zero above the plane, the potential energy is also zero. So to move a link of the chain from one side of the plane to the other, you need to apply a force (and put in enough energy to overcome the potential). So your chain is not in free-fall with an acceleration g - you have to remove the acceleration due to the force at the barrier. So it is not very suprising that you energy is not conserved - you have missed a bit. However, you may be thinking instead of the potential not being zero above the plane, but just flat (so there is still no apparent force). Then you don't need to expand much energy pushing the links of the chain over the edge. Physically you could think of this as the chain being on a high up shelf of ice. One link falls off (blown by the wind or something) and the rest follows. But that is a perfectly normal scenario and I have even seen it used as an exam question. There is no conservation of energy problem there. Neglecting air resistance, each link will hit the ground with a speed [math]v=\sqrt{2gh}=\sqrt{2 \times 9.81 {\rm ms}^{-2} \times 20 {\rm m}} = 19.8 {\rm ms}^{-1}[/math] just like usual, conserving energy.

And what impact do these ideas have that makes him "one of the world's greatest scientists of all time"? I think you are either very ignorant of science or have a very warped sense of what is important.

One reason why a lot of people don't like her is because she is a strong woman. There is still a large part of the population that thinks a woman should be demure and placid, staying in the home, and don't like a woman who takes charge.

Not really. String theory doesn't have much to say about the [math]J/\psi[/math].

For the dark matter doubters, you might like to explain how your favourite model can explain the Bullet Cluster better than Dark Matter. Radiating matter is in red; gravitating matter is in blue.

He is a physicist. He was probably trying it on his own.

I should also point out that Dawkins' employer, the University of Oxford, is not a private organisation. It is a state university and funded by the state.

Are you sure it isn't just that it is the same people on all the time?

That is exactly the problem! He does not follow his own advice. He promotes his own private feelings as if they were scientific fact, when they are nothing more than opinion. I really wouldn't have a problem with the man if he were just some ordinary Joe in the street writing rants about religion, but he is not. He is an Oxford Professor for the Public Understanding of Science, and as such his opinion carries a weight and a responsibility to not mislead people about science. When presenting a personal opinion he has to be completely clear that it is an opinion and not a scientific statement otherwise a large portion of the public will accept his word as true without thinking. That is exactly the thing he blaims religion for yet he sees no problem with blind acceptance when it is acceptance of his beliefs.

There is actually no such thing as negative mass by construction. If you mean negative gravitational mass (which is not what the original post is suggesting) then you can't have it because of the structure of GR. If you mean negative inertial mass (which appears to be what is intended in the OP) you either can't have them, or always have them, depending on your point of view. There are two types of masses in our fundamental theories - bosonic and fermion masses. Bosonic masses (like for the Z-boson or the Higgs) always appear in the equations as their square [math]m^2[/math] so having negative mass is exactly the same as a positive mass (you couldn't tell the difference, so there is no difference). For fermions (eg the electron) it is similar - although the mass now appears unsquared, one can always redefine the fermion fields themselves (actually a rotation in the complex plane) to absorb the minus sign. So again, there is no difference.

The information paradox is not really much of a worry in my opinion because we do not have a consistent theory of gravity at the quantum scale. Once we have one, if the problem persists then it will be serious. But who knows what quantum weirdness we will have to come up with to explain gravity...

Faculty If you can't do calculations, then you can't make predictions. And if you can't make predictions, you are not doing science - just pointless navel gazing.

I am writing a paper about the neutralino right now as a matter of fact.